Stacked structure

ABSTRACT

A stacked structure for patterning a material layer to form an opening pattern with a predetermined opening width in the layer is provided. The stacked structure includes an underlayer, a silicon rich organic layer, and a photoresist layer. The underlayer is on the material layer. The silicon rich organic layer is between the underlayer and the photoresist layer. The thickness of the photoresist layer is smaller than that of the underlayer and larger than two times of the thickness of the silicon rich organic layer. The thickness of the underlayer is smaller than three times of the predetermined opening width.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 11/464,496,filed Aug. 15, 2006, and incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor process. Moreparticularly, the present invention relates to a stacked structure and apatterning method using the stacked structure.

2. Description of the Prior Art

In a semiconductor process, usually the pattern is formed on thephotoresist layer in a process of lithography. Then, the photoresistlayer serves as the etching mask to perform the dry or wet etchingprocess so as to transfer the pattern in the photoresist layer to thelayer to be patterned beneath the photoresist layer. Along with the highintegration of semiconductor devices, the manufacturing criticaldimension (CD) of the integrated circuit increasingly becomes small.Therefore, the resolution required by lithography becomes high. In orderto satisfy the demands for high resolution, the thickness of thephotoresist layer is gradually reduced. However, if the thickness of thephotoresist layer is too thin, in the subsequent etching process, it ispossible that the photoresist layer serving as the etching mask iscompletely etched before completely transferring the pattern to thelayer to be patterned beneath the photoresist layer. Therefore, it isurgent to find a way to completely transfer the pattern to the layerthereunder by the use of the thin photoresist layer.

SUMMARY OF THE INVENTION

Accordingly, the objective of the present invention is to provide apatterning method using the thin photoresist layer to transfer thepattern.

Another objective of the present invention is to provide a stackedstructure applicable to the patterning process, for patterning thematerial layer with a smaller line width.

The present invention provides a method for patterning a material layerto form an opening pattern with a predetermined opening width in thematerial layer. In the method, an underlayer, a silicon rich organiclayer, and a photoresist layer are sequentially formed on the substrateformed with a material layer. The thickness of the photoresist layer islarger than two times of the thickness of the silicon rich organiclayer, but is smaller than the thickness of the underlayer. Then, thephotoresist layer is patterned to form the opening pattern in thephotoresist layer. Next, the silicon rich organic layer is etched withthe photoresist layer serving as a mask, so as to transfer the openingpattern to the silicon rich organic layer. Thereafter, the underlayer isetched with the silicon rich organic layer serving as the mask, so as totransfer the opening pattern to the underlayer. When the opening patternis completely transferred to the underlayer, the photoresist layer iscompletely etched. Then, the material layer is etched with theunderlayer serving as the mask, so as to transfer the opening pattern tothe material layer. When the opening pattern is completely transferredto the material layer, the silicon rich organic layer is completelyetched.

According to an embodiment of the present invention, a hard mask layerwith the thickness slightly larger than the thickness of the siliconrich organic layer is further provided between the material layer andthe underlayer. After etching the underlayer and before etching thematerial layer, the method further comprises etching the hard mask layerwith the silicon rich organic layer and the underlayer serving as themask, so as to transfer the opening pattern to the hard mask layer. Whenthe opening pattern is completely transferred to the hard mask layer,the silicon rich organic layer is completely etched.

According to an embodiment of the present invention, the thickness ofthe underlayer is smaller than three times of the predetermined openingwidth.

According to an embodiment of the present invention, after forming theopening pattern in the photoresist layer and before transferring theopening pattern to the silicon rich organic layer, and/or after etchingthe hard mask layer and before transferring the opening pattern to thematerial layer, the method further comprises a trimming step to changethe width of the opening pattern.

According to an embodiment of the present invention, the material layercomprises a conductive layer, and the method further comprises etchingthe conductive layer with the underlayer serving as the mask, so as totransfer the opening pattern to the conductive layer, and then removingthe underlayer.

According to another embodiment of the present invention, a conductivelayer is further provided between the material layer and the substrate,and the method further comprises removing the underlayer, and thentransferring the opening pattern to the conductive layer with the hardmask layer serving as the mask.

According to an embodiment of the present invention, the material of thehard mask layer comprises silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, silicon oxycarbide, and siliconcarbonitride.

According to an embodiment of the present invention, the thickness ofthe photoresist layer is about 500 to 2000 Å, the thickness of thesilicon rich organic layer is about 250 to 500 Å, the thickness of theunderlayer is about 1000 to 2500 Å, and the thickness of the mask layeris about 250 to 900 Å.

According to an embodiment of the present invention, the thickness ofthe underlayer is smaller than three times of the predetermined openingwidth.

According to an embodiment of the present invention, the siliconcontaining organic layer is formed by spin-coating, and the thickness isthe minimum thickness formed by spin-coating.

According to an embodiment of the present invention, the material of thesilicon rich organic layer comprises the silicon polymer with thesilicon content of 5-30 wt. %.

According to an embodiment of the present invention, the underlayercomprises varnish resin, for example, an I-line photoresist layer.

According to an embodiment of the present invention, the method forpatterning the photoresist layer comprises exposing in a process ofimmersion lithography, and the photoresist layer is a waterproofphotoresist layer, or a photoresist material layer covered by awaterproof layer on the top thereof.

According to an embodiment of the present invention, after forming theopening pattern in the photoresist layer and before transferring theopening pattern to the silicon rich organic layer, and/or after etchingthe underlayer and before transferring the opening pattern to thematerial layer, the method further comprises a trimming step to changethe opening width of the opening pattern.

The present invention further provides a stacked structure forpatterning a material layer to form an opening pattern with apredetermined opening width in the material layer. The structurecomprises an underlayer, a silicon rich organic layer, and a photoresistlayer. The underlayer is disposed on the material layer; the siliconrich organic layer is disposed between the underlayer and thephotoresist layer, and the thickness of the photoresist layer is largerthan two times of the thickness of the silicon rich organic layer, butis smaller than the thickness of the underlayer.

According to an embodiment of the present invention, the thickness ofthe underlayer is smaller than three times of the predetermined openingwidth.

According to an embodiment of the present invention, the stackedstructure further comprises a hard mask layer disposed between thematerial layer and the underlayer, and the thickness of the hard masklayer is slightly larger than the thickness of the silicon rich organiclayer.

According to an embodiment of the present invention, the material of thehard mask layer comprises silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, silicon oxycarbide, and siliconcarbonitride.

According to an embodiment of the present invention, the material of theunderlayer comprises varnish resin, for example, the I-line photoresistlayer.

In the present invention, by carefully arranging the configuration orderand thickness of each layer in the stacked structure, and by using thecharacteristic of difference in etching selectivity of the layers, thequite thin photoresist layer can be used to transfer the pattern.Therefore, it is quite suitable for the process of semiconductor devicewith small line width.

In order to the make aforementioned and other objects, features andadvantages of the present invention comprehensible, preferredembodiments accompanied with figures are described in detail below.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E are schematic cross-sectional views of a patterningmethod using a stacked structure according to an embodiment of thepresent invention.

FIGS. 2A to 2E are schematic cross-sectional views of a method ofpatterning the gate conductive layer by using the stacked structureaccording to an embodiment of the present invention.

FIGS. 3A to 3F are schematic cross-sectional views of a patterningmethod using a stacked structure according to another embodiment of thepresent invention.

FIGS. 4A to 4F are schematic cross-sectional views of a method offorming the trench of the shallow trench isolation (STI) by using thestacked structure according to another embodiment of the presentinvention.

DETAILED DESCRIPTION

FIGS. 1A to 1E are schematic cross-sectional views of a patterningmethod using a stacked structure according to an embodiment of thepresent invention.

Referring to FIG. 1A, the present invention provides a stacked structure150 for patterning a material layer 102 to form an opening pattern 112in the material layer 102 on the substrate 100. The opening pattern 112has a predetermined opening width W1. The stacked structure comprises anunderlayer 106, a silicon rich organic layer 108, and a photoresistlayer 110. The underlayer 106 is disposed on the material layer 102, andthe silicon rich organic layer 108 is disposed between the underlayer106 and the photoresist layer 110.

The photoresist layer 110 comprises a positive photoresist or a negativephotoresist, which is a photoresist material usually used in aconventional lithography process, or a waterproof photoresist layer usedin an immersion lithography process, or a photoresist material layercovered by a waterproof layer on the top thereof. The thickness of thephotoresist layer 110 is smaller than the thickness of the underlayer106, but is larger than two times of the thickness of the silicon richorganic layer 108. The material of the silicon rich organic layer 108comprises an organic silicon material for the bottom antireflectivecoating (BARC), for example, a silicon polymer with the silicon contentof 5-30 wt. %, disclosed in U.S. Pat. No. 6,025,117, which isincorporated herein by reference. The method of forming the silicon richorganic layer 108 is, for example, spin-coating. In an embodiment, thethickness of the silicon rich organic layer 108 is the minimum thicknessformed by the spin-coating. The material of the underlayer 106 comprisesvarnish resin, for example, an I-line photoresist layer. In anembodiment, the thickness of the underlayer 106 is smaller than threetimes of the predetermined opening width W1.

Referring to FIG. 1B, when the stacked structure 150 is used to patternthe material layer 102, the photoresist layer 110 is patterned first, soas to form an opening pattern 114 in the photoresist layer 110. Themethod of patterning the photoresist layer 110 can adopt theconventional lithography process, or the immersion lithography processto perform an exposure process and then a development process, so as toform the opening pattern 114.

If it is inspected that the opening pattern 114 in the photoresist layer110 cannot form an opening with the same width W1 as that of thepredetermined opening 112 in the subsequent process after development, atrimming step for the opening width can be performed before etching thesilicon rich organic layer 108, so as to satisfy the requirement for thewidth of the opening pattern 114.

Next, the silicon rich organic layer 108 is etched with the photoresistlayer 110 serving as the mask, so as to transfer the opening pattern 114to the silicon rich organic layer 108. The etching method can be dryetching. During the etching process, the photoresist layer 110 loses dueto the etching. When the opening pattern 114 is completely transferredto the silicon rich organic layer 108, a small part of the photoresistlayer 110 remains on the silicon rich organic layer 108.

Then, referring to FIG. 1C, the underlayer 106 is etched with thephotoresist layer 110 and the silicon rich organic layer 108 serving asthe mask, so as to transfer the opening pattern 114 to the underlayer106. When the opening pattern 114 is completely transferred to theunderlayer 106, the photoresist layer 110 is completely etched.

Then, referring to FIG. 1D, the material layer 102 is etched with thesilicon rich organic layer 108 serving as the mask, so as to transferthe opening pattern 114 to the material layer 102. When the openingpattern 114 is completely transferred to the material layer 102, thesilicon rich organic layer 108 is completely etched. If the silicon richorganic layer 108 is completely etched during the etching process, theunderlayer 106 serves as the etching mask to continue etching until theopening pattern 114 is completely transferred to the material layer 102.The method of etching the material layer 102 is, for example, dryetching, and the etching gas varies in accordance with the materiallayer 102 to be etched.

Then, referring to FIG. 1E, the underlayer 106 is removed. The method ofremoving the underlayer 106 is dry removing or wet removing.

In the stacked structure of the present invention, the stacking sequenceand the thickness of each layer are carefully considered, and thedetails will be illustrated as follows.

The Photoresist Layer:

After the silicon rich organic layer 108 is patterned, when the patternis transferred to the underlayer 106 thereunder, the etching selectivityratio between the silicon rich organic layer 108 and the underlayer 106is quite high, so the thickness of the silicon rich organic layer isrequired to be quite thin, for example the minimum thickness formed byspin-coating. Therefore, the thickness of the photoresist layer on thesilicon rich organic layer is required to be sufficient to serve as themask for etching the silicon rich organic layer, so as to successfullytransfer the pattern to the silicon rich organic layer thereunder.Therefore, the present invention can adopt the photoresist layer havinga quite thin thickness, and can adopt the exposing light source having arelatively short wavelength to fabricate the device with small linewidth.

The Silicon Rich Organic Layer:

After the pattern is transferred to the underlayer 106, when thematerial layer 102 below the underlayer 106 is etched, the thickness ofthe silicon rich organic layer 108 serving as the top mask layer isquite thin, so before completely transferring the pattern to thematerial layer 102, the silicon rich organic layer 108 is completelyetched. Thus, after completely transferring the pattern to the materiallayer 102, the silicon rich organic layer 108 does not remain on theunderlayer 106. Therefore, subsequently, the problems that the remainingsilicon rich organic layer 108 is difficult to be removed, or duringremoving, the etchant damages the opening pattern of the material layer102 or damages the substrate do not exist.

The Underlayer:

After the pattern is transferred to the underlayer 106, when thematerial layer 102 below the underlayer 106 is etched, even if thesilicon rich organic layer 108 is completely etched before the patternis completely transferred to the material layer 102, because theunderlayer 106 has the enough thickness, the pattern can be successfullytransferred to the material layer 102. In another aspect, because thethickness of the underlayer 106 is not larger than three times of thepredetermined opening width, i.e. when the material layer 102 is etched,the aspect ratio of the opening formed in the underlayer 106 and thematerial layer 102 is smaller than 3. Thus, the opening pattern 114 canbe completely transferred to the material layer 102, and the problemthat the opening cannot be formed due to the incomplete etching does notexist.

The stacked structure and the patterning method can be applied in theprocess of patterning the dielectric layer or the conductive layer. Theprocess method of the gate conductive layer is taken as an example forillustration with reference to FIGS. 2A to 2E in the following.

Referring to FIG. 2A, a substrate 200 is provided. The substrate 200 hasa gate dielectric layer 201 and a gate conductive layer 202. A pluralityof gaps 212 is predetermined to be formed in the gate conductive layer202, and the predetermined width of the gap 212 is W2. The gateconductive layer 202 is, for example, a doped polysilicon layer, or apolysilicon metal layer composed of the doped polysilicon layer and thesilicon metal layer. The stacked structure 250 comprises an underlayer206, a silicon rich organic layer 208, and a photoresist layer 210. Thephotoresist layer 210 can adopt the positive photoresist or the negativephotoresist, and the thickness thereof is about 500 to 2000 Å. Thesilicon rich organic layer 208 can adopt the silicon polymer with thesilicon content of 5-30 wt. %, disclosed in U.S. Pat. No. 6,025,117, andthe thickness thereof is about 250 to 500 Å. The material of theunderlayer 206 is, for example, the I-line photoresist layer, and thethickness thereof is about 2000 to 2500 Å.

In an embodiment, the width W2 of the gap 212 between the patternedconductive layers to be formed is 65 nm. The thickness of the siliconrich organic layer 208 is 300 Å. The thickness of the photoresist layer210 is larger than 600 Å. The thickness of the underlayer 206 is smallerthan 1950 Å. In another embodiment, the width W2 of the gap 212 betweenthe patterned conductive layers to be formed is 55 nm. The thickness ofthe silicon rich organic layer 208 is 300 Å. The thickness of thephotoresist layer 210 is larger than 600 Å. The thickness of theunderlayer 206 is smaller than 1650 Å. In still another embodiment, thewidth W2 of the gap 212 between the patterned conductive layers to beformed is 45 nm. The thickness of the silicon rich organic layer 208 is300 Å. The thickness of the photoresist layer 210 is larger than 600 Å.The thickness of the underlayer 206 is smaller than 1350 Å.

Referring to FIG. 2B, when the conductive layer 202 is patterned byusing the stacked structure 250, the photoresist layer 210 is patternedfirst, so as to form the opening pattern 214 in the photoresist layer210. The method of patterning the photoresist layer 210 can adopt theconventional lithography process, or can adopt the immersion lithographyprocess to perform the exposure process and then the development processto form the opening pattern 214.

If it is inspected that the opening pattern 214 in the photoresist layer210 cannot form an gap with the same width W2 as that of thepredetermined gap 212 in the subsequent process after development, astep of trimming the gap width can be performed before etching thesilicon rich organic layer 208, so as to satisfy the requirement for thewidth of the opening pattern 214. In the trimming step, CF₄ and hydrogenbromide act as the reaction gas to etch the photoresist layer 110.

Then, the silicon rich organic layer 208 is etched with the photoresistlayer 210 serving as the mask, so as to transfer the opening pattern 214to the silicon rich organic layer 208. The etching method can adopt thedry etching by using, for example, fluorine-containing gas, such asperfluorinated compound as the etching gas.

Then, referring to FIG. 2C, the underlayer 206 is etched with thephotoresist layer 210 and the silicon rich organic layer 208 serving asthe mask, so as to transfer the opening pattern 214 to the underlayer206. The etching method can adopt the dry etching by using, for example,gas containing oxygen, carbon monoxide, chlorine, and argon as theetching gas. When the opening pattern 214 is completely transferred tothe underlayer 206, the photoresist layer 210 is completely etched.

Then, referring to FIG. 2D, the conductive layer 202 is etched with thesilicon rich organic layer 208 serving as the mask, so as to transferthe opening pattern 214 to the conductive layer 202. When the openingpattern 214 is completely transferred to the conductive layer 202, thesilicon rich organic layer 208 is completely etched. If the silicon richorganic layer 208 is completely etched during the etching process, theunderlayer 206 serves as the etching mask to continue etching until theopening pattern 214 is completely transferred to the conductive layer202. The method of etching the material layer 202 is, for example, thedry etching, and the etching gas is, for example, perfluorocarbon orSF₆.

Then, referring to FIG. 2E, the underlayer 206 is removed, such that thepatterned conductive layer 202 is exposed. The method of removing theunderlayer 206 can adopt the dry removing, for example, O₂ plasmaashing.

FIGS. 3A to 3F are schematic cross-sectional views of a patterningmethod using a stacked structure according to another embodiment of thepresent invention.

Referring to FIG. 3A, the present invention provides a stacked structure360 for patterning a material layer 302 to form a predetermined openingpattern 312 in the material layer 302. The opening pattern 312 has apredetermined opening width W3. The stacked structure comprises a hardmask layer 304, an underlayer 306, a silicon rich organic layer 308, anda photoresist layer 310. The hard mask layer 304 is disposed on thematerial layer 302. The underlayer 306 is disposed on the hard masklayer 304. The silicon rich organic layer 308 is disposed between theunderlayer 306 and the photoresist layer 310. The thickness of the hardmask layer 304 is slightly larger than the thickness of the silicon richorganic layer 308. The thickness of the photoresist layer 310 is smallerthan the thickness of the underlayer 306, but is larger than two timesof the thickness of the silicon rich organic layer 308.

The photoresist layer 310 comprises the positive photoresist or thenegative photoresist, which is the photoresist material usually used inthe conventional lithography process, or the waterproof photoresistlayer used in the immersion lithography process, or the photoresistmaterial layer covered by a waterproof layer on the top thereof. Thematerial of the silicon rich organic layer 308 comprises thesilicon-containing organic hard mask material for the bottomantireflective coating (BARC), for example, the silicon polymer with thesilicon content of 5-30 wt. %, disclosed in U.S. Pat. No. 6,025,117,which is incorporated herein by reference. The forming method is, forexample, the spin-coating. In an embodiment, the thickness of thesilicon rich organic layer 308 is the minimum thickness formed byspin-coating. The material of the underlayer 306 comprises the varnishresin, for example, the I-line photoresist layer. In an embodiment, thethickness of the underlayer 306 is smaller than three times of thepredetermined opening width W3. The material of the hard mask layer 304is, for example, silicon oxide, silicon nitride, silicon oxynitride,silicon carbide, silicon oxycarbide, or silicon carbonitride. Theforming method can adopt chemical vapor deposition.

Referring to FIG. 3B, when the material layer 302 is patterned by usingthe stacked structure 360, the photoresist layer 310 is patterned first,so as to form the opening pattern 314 in the photoresist layer 310. Themethod of patterning the photoresist layer 310 can adopt theconventional lithography process, or can adopt the immersion lithographyprocess to perform the exposure process and the development process toform the opening pattern 314.

If it is inspected that the opening pattern 314 in the photoresist layer310 can not form an opening with the same width W3 as that of thepredetermined opening 312 in the subsequent process after development, astep of trimming the opening width can be carried out before etching thesilicon rich organic layer 308, so as to satisfy the requirement for thewidth of the opening pattern 314.

Then, the silicon rich organic layer 308 is etched with the photoresistlayer 310 serving as the mask, so as to transfer the opening pattern 314to the silicon rich organic layer 308. The etching method can adopt thedry etching by using, for example, the fluorine-containing gas, such asthe perfluorinated compound as the etching gas. During the etchingprocess, the photoresist layer 310 loses due to the etching. When theopening pattern 314 is completely transferred to the silicon richorganic layer 308, a small part of the photoresist layer 310 remains onthe silicon rich organic layer 308.

Then, referring to FIG. 3C, the underlayer 306 is etched with thephotoresist layer 310 and the silicon rich organic layer 308 as themask, so as to transfer the opening pattern 314 to the underlayer 306.The etching method of can adopt the dry etching. When the openingpattern 314 is completely transferred to the underlayer 306, thephotoresist layer 310 is completely etched.

Then, referring to FIG. 3D, the hard mask layer 304 is etched with thesilicon rich organic layer 308 and the underlayer 306 as the mask, so asto transfer the opening pattern 314 to the hard mask layer 304. When theopening pattern 314 is completely transferred to the hard mask layer304, the silicon rich organic layer 308 is completely etched.

After the hard mask layer 304 is etched, when it is found that theopening pattern 314 in the hard mask layer 304 cannot form an openingwith the same width W3 as that of the predetermined opening 312 in thesubsequent process, a step of trimming the opening width can beperformed before etching the material layer 302, so as to satisfy therequirement for the width of the opening pattern 314. During thetrimming step, the removing rates of the underlayer 306 and the hardmask layer 304 must be approximately the same, so as to assure theconsistency of the opening patterns 314 of the two.

Then, referring to FIG. 3E, the underlayer 306 is removed. The method ofremoving the underlayer 306 is dry removing or wet removing. The dryremoving can adopt the O₂ plasma ashing. Then, the material layer 302 isetched with the hard mask layer 304 serving as the mask, so as totransfer the opening pattern 314 to the material layer 302, as shown inFIG. 3F.

Referring to FIG. 3EE, another method involves after the opening pattern314 is completely transferred to the hard mask layer 304, etching thematerial layer 302 with the underlayer 306 serving as the mask, so as totransfer the pattern 314 to the material layer 302. If the underlayer306 is completely etched during the etching process, the hard mask layer304 serves as the mask to continue etching until the opening pattern 314is completely transferred to the material layer 302. If the underlayer306 is not completely etched during the etching process, after theopening patter 314 is completely transferred to the material layer 302,the underlayer 306 is removed, as shown in FIG. 3F.

In the stacked structure of the present invention, the stacking sequenceand the thickness of each layer are carefully considered, and thedetails will be illustrated as follows.

The Photoresist Layer:

After the silicon rich organic layer 308 is patterned, when the patternis transferred to the underlayer 306 thereunder, the etching selectivityratio between the silicon rich organic layer 308 and the underlayer 306is quite high, so the thickness of the silicon rich organic layer 308 isrequired to be quite thin, for example, the minimum thickness formed byspin-coating. Therefore, the thickness of the photoresist layer 310 onthe silicon rich organic layer 308 is required to be sufficient to serveas the mask for etching the silicon rich organic layer 308, so as tosuccessfully transfer the pattern to the silicon rich organic layer 308thereunder. Therefore, the photoresist layer has a quite thin thickness,and the exposing light source having a relatively short wavelength canbe adopted to fabricate the device with small line width.

The Silicon Rich Organic Layer:

After the pattern is transferred to the underlayer 306, when the hardmask layer 304 is etched, the thickness of the silicon rich organiclayer 308 serving as the top mask layer is thinner than the thickness ofthe hard mask layer. Therefore, if the etchant having substantially thesame etching rate for the two is selected during the etching process,before the pattern is completely transferred to the hard mask layer 304,the silicon rich organic layer 308 is completely etched. Thus, after thepattern is completely transferred to the hard mask layer 304, no siliconrich organic layer remains on the underlayer 306. Therefore,subsequently, the problems that the remaining silicon rich organic layeris difficult to be removed, or during removing, the etchant damages theopening pattern of the hard mask layer 304 do not exist.

The Underlayer:

After the pattern is transferred to the underlayer 306, when the hardmask layer below the underlayer 306 is etched, even if the silicon richorganic layer 308 is completely etched before the pattern is completelytransferred to the hard mask layer 304, because the underlayer 306 hasenough thickness, the pattern can be successfully transferred to thematerial layer 302. In another aspect, because the thickness of theunderlayer 306 is not larger than three times of the predetermined widthW3 of the opening 312, i.e. when the hard mask layer 304 is etched, theaspect ratio of the opening 314 formed in the underlayer 306 and thehard mask layer 304 is smaller than 3. Thus, the opening pattern 314 canbe completely transferred to the hard mask layer 304, and the problemthat the opening cannot be formed due to the incomplete etching does notexist.

The Hard Mask Layer:

In order to avoid the incomplete etching, preferably the thickness ofthe underlayer 306 is not larger than three times of the width W3 of theopening 312. However, if the hard mask layer 304 does not exist, and thedepth of the opening 312 to be formed in the material layer 302 isrelatively deep, the underlayer 306 must have enough thickness to serveas the etching mask. Otherwise, before the opening depth formed in thematerial layer 302 reaches the required depth, the underlayer 306 iscompletely etched. The advantage of adding a hard mask 304 on theunderlayer 306 and the material layer 302 is that even if the underlayer306 is completely etched during the process of etching the materiallayer 302, the etching rate of the hard mask layer 304 smaller than thatof the material layer 302 and far smaller than that of the underlayer306 such that the hard mask layer 304 can serve as the mask, and thusthe required opening may be successfully formed in the material layer302.

The stacked structure and the patterning method can be applied in thegate conductive layer or the STI process, but it is not limited herein.The method applied in the STI is illustrated in detail with reference toFIGS. 4A to 4F as follows.

Referring to FIG. 4A, a substrate 402 is provided. A plurality oftrenches 412 is preformed in the substrate 402, and the predeterminedwidth of the trench 412 is W4. The substrate 402 is, for example,entirely a semiconductor substrate, such as silicon, germanium, SiGe,SiC, or silicon on insulator (SOI). Then, a pad oxide layer 403 and astacked structure 460 are formed on the substrate 402. The stackedstructure 460 comprises a hard mask layer 404, an underlayer 406, asilicon rich organic layer 408, and a photoresist layer 410. Thephotoresist layer 410 can adopt the positive photoresist or the negativephotoresist, and the thickness thereof is about 500 to 2000 Å. Thesilicon rich organic layer 408 can adopt the silicon polymer with thesilicon content of 5-30 wt. %, disclosed in U.S. Pat. No. 6,025,117, thethickness thereof is about 250 to 500 Å. The material of the underlayer406 is, for example, the I-line photoresist layer, and the thicknessthereof is about 1000 to 2500 Å. The material of the hard mask layer 404is, for example, silicon nitride, and the forming method can adopt thechemical vapor deposition, and the thickness thereof is slightly largerthan the thickness of the silicon rich organic layer 408, and is forexample, about 250 to 900 Å.

Referring to FIG. 4B, when the substrate 402 is patterned by using thestacked structure 460, the photoresist layer 410 is patterned first, soas to form the trench pattern 414 in the photoresist layer 410. Themethod of patterning the photoresist layer 410 can adopt theconventional lithography process, or can adopt the immersion lithographyprocess to perform the exposure process and then the development processto form the trench pattern 414.

If it is inspected that the trench pattern 414 in the photoresist layer410 cannot form a trench with the predetermined width W4 in thesubsequent process after development, a step of trimming the trenchwidth can be performed before etching the silicon rich organic layer408, so as to satisfy the requirement for the width of the trenchpattern 414. The trimming step 120 can use CF₄ and hydrogen bromide asthe reaction gas.

Then, the silicon rich organic layer 408 is etched with the photoresistlayer 410 serving as the mask, so as to transfer the trench pattern 414to the silicon rich organic layer 408. The etching method can adopt thedry etching by using, for example, the fluorine-containing gas, such asthe perfluorinated compound as the etching gas. During the etchingprocess, the photoresist layer 410 loses due to the etching. Therefore,when the trench pattern 414 is completely transferred to the siliconrich organic layer 408, a small part of the photoresist layer 410remains on the silicon rich organic layer 408, or is completely etched.

Then, referring to FIG. 4C, the underlayer 406 is etched with thesilicon rich organic layer 408 as the mask, so as to transfer the trenchpattern 414 to the underlayer 406. The etching method can adopt the dryetching, for example, the gas containing oxygen, carbon monoxide,chlorine, and argon as the etching gas. When the trench pattern 414 iscompletely transferred to the underlayer 406, the photoresist layer 410is completely etched.

Then, referring to FIG. 4D, the hard mask layer 404 is etched with thesilicon rich organic layer 408 and the underlayer 406 as the mask, so asto transfer the trench pattern 414 to the hard mask layer 404. Duringetching, the etchant having substantially the same etching rate for thesilicon rich organic layer 408 and the hard mask layer 404 is selectedfor etching. Because the thickness of the silicon rich organic layer 408is smaller than the thickness of the hard mask layer 404, when thetrench pattern 414 is completely transferred to the hard mask layer 404,the silicon rich organic layer 408 is completely etched, and no siliconrich organic layer 408 remains on the underlayer 406.

After the hard mask layer 404 is etched, it is found that the trenchpattern 414 in the hard mask layer 404 cannot form a trench 412 with thepredetermined width W4 in the subsequent process, a step of trimming thetrench width can be performed before etching the silicon substrate 402,so as to satisfy the requirement for the width of the trench pattern414. During the trimming step, the removing rates of the underlayer 406and the hard mask layer 404 must be substantially the same, so as toassure the consistency of the trench pattern 414 of the two. Thetrimming step can use CF₄ and trifluoromethane as the reaction gas toperform etching, thus complete trimming.

Then, referring to FIG. 4E, the underlayer 406 is removed. The method ofremoving the underlayer 406 can adopt the dry removing or the wetremoving. The dry removing can adopt the O₂ plasma ashing. Then, the padoxide layer 403 and the substrate 402 are etched by using the hard masklayer 404 as the mask, so as to transfer the trench pattern 414 to thesubstrate 402, as shown in FIG. 4F. The method of etching the substrate402 can adopt the dry etching by using, for example, perfluorocarbon orSF₆ as the etching reaction gas.

Referring to FIG. 4EE, another method involves after the trench pattern414 is completely transferred to the hard mask layer 404, beforeremoving the underlayer 406, etching the substrate 402 with theunderlayer 406 serving as the mask, so as to transfer the openingpattern 414 to the substrate 402 to form the trench. If the underlayer406 is completely etched during the etching process, the hard mask layer404 serves as the mask to continue etching until the trench pattern 414is completely transferred to the substrate 402. If the underlayer 406 isnot completely etched during the etching process, after the trenchpattern 414 is completely transferred to the substrate 402, theunderlayer 406 is removed, as shown in FIG. 4F.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A stacked structure for patterning a material layer to form anopening pattern with a predetermined opening width in the materiallayer, comprising: an underlayer, disposed on the material layer; asilicon rich organic layer, disposed on the underlayer; and aphotoresist layer, disposed on the silicon rich organic layer, thethickness of the photoresist layer being larger than two times of thethickness of the silicon rich organic layer, but is smaller than thethickness of the underlayer.
 2. The stacked structure for patterning asclaimed in claim 1, wherein the thickness of the underlayer is smallerthan three times of the predetermined opening width.
 3. The stackedstructure for patterning as claimed in claim 1, further comprising ahard mask layer disposed between the material layer and the underlayer,the thickness of the hard mask layer being slightly larger than thethickness of the silicon rich organic layer.
 4. The stacked structurefor patterning as claimed in claim 3, wherein the thickness of theunderlayer is smaller than three times of the predetermined openingwidth.
 5. The stacked structure for patterning as claimed in claim 3,wherein the material of the hard mask layer comprises silicon oxide,silicon nitride, silicon oxynitride, silicon carbide, siliconoxycarbide, and silicon carbonitride.
 6. The stacked structure forpatterning as claimed in claim 1, wherein the underlayer comprisesvarnish resin.
 7. The stacked structure for patterning as claimed inclaim 6, wherein the underlayer comprises the I-line photoresist layer.